Electric motors and other electrical drive units are used in a variety of contexts. For example, some vehicles have one or more electric motors or used for propelling the vehicle. Such motor(s) can be the vehicle's sole traction mode, as in a pure electric vehicle, or it/they can be used in combination with another traction mode, such as in a hybrid vehicle.
Electric motors generate heat when operated. If the amount of generated heat is greater than what is naturally dissipated to the environment through the motor's housing or other exterior feature, some form of active cooling can be provided. The active cooling can be driven directly by the rotational energy of the motor, or by external power, such as electricity. Typically, the active cooling is applied to one or more heat-generating parts of the motor, and/or the heat-sensitive part(s), so that unsafe temperatures are avoided. In the case of the stator and rotor of an electric motor, they typically consist of complex surfaces and structures—rotating structures in the case of the rotor—all of which generate some amount of heat during operation.